BlaGES carrying Pseudomonas aeruginosa isolates from a public hospital in Rio de Janeiro, Brazil

Unravelling complex transposable elements surrounding blaGES-16 in a Pseudomonas aeruginosa ExoU strain

OBJECTIVES

We characterised the complex surrounding regions of bla_GES-16 in a Pseudomonas aeruginosa exoU+ strain (P-10.226) in Brazil.

METHODS

Species identification was performed by MALDI-TOF MS, and the antimicrobial susceptibility profile was determined by broth microdilution based on European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints. The whole genome sequencing (WGS) of P-10.226 strain was performed using both short-read paired-end sequencing on the Illumina MiSeq platform as well as the long-read Oxford Nanopore MinION.

RESULTS

WGS analysis showed that P-10.226 carried bla_GES-16, which was found as a gene cassette inserted into a novel class I integron, In1992 (aadB-bla_OXA-56-bla_GES-16-aadB-aadA6c), whose 3'-CS was truncated by a nested transposable element, IS5564::ISPa157. The structure was even more complex since IS6100-ΔIS6100 structure and a TnAs2-like harbouring the operon merRTPADE was found downstream In1992. Fragments of TnAs3 harbouring 25-bp imperfect inverted repeats were identified bordering the intl1 of In1992 and also flanking IS6100-ΔIS6100, which might be genetic marks of its previous presence in the genome. Interestingly, In1992 also shows a distinct cassette array from In581 (bla_GES-16-dfrA22-aacA27-aadA1), which was previously reported in Serratia marcescens strains recovered in Brazil. Finally, exoU gene, which encodes a potent cytotoxin of type III secretion systems (T3SS) effector proteins from P. aeruginosa and is associated to severe infections, was also detected.

CONCLUSION

We described the novel In1992 carrying bla_GES-16 surrounded by complex transposition events in a XDR P. aeruginosa strain. The identification of many sets of direct repeats adjacent to TnAs3 fragments indicates a major past of transposition events that shaped the current genetic environment of In1992.

Extensively drug-resistant (XDR) Pseudomonas aeruginosa identified in Lima, Peru co-expressing a VIM-2 metallo-β-lactamase, OXA-1 β-lactamase and GES-1 extended-spectrum β-lactamase

Introduction

Pseudomonas aeruginosa has the ability to acquire plasmids and other mobile genetic elements that confer resistance to antibiotics. Bacterial genes encoding different β-lactamases (bla), such as metallo-β-lactamases (MBLs) and extended-spectrum β-lactamases (ESBL), can confer resistance to multiple classes of β-lactam antibiotics.

Case presentation

An 83 year old female was admitted in 2012 to the Peruvian Naval Hospital, Centro Médico Naval 'Cirujano Mayor Santiago Távara' (CEMENA), in Lima, Peru. A midstream urine sample was collected and sent to the local CEMENA laboratory for routine urine culture. P. aeruginosa was isolated and initial antibiotic susceptibility testing showed it to be sensitive to imipenem. The clinicians started a course of meropenem, but the patient did not improve. After 5 days, a second urine culture was performed and a P. aeruginosa was isolated again, but this time the strain showed resistance to imipenem. The treatment course was changed to fosfomycin and the patient improved. Phenotypic and molecular laboratory testing to characterize the antibiotic resistance were performed, demonstrating the presence of both MBL and ESBL genes.

Conclusion

To our knowledge, this is the first report of a P. aeruginosa XDR clinical isolate that co-expresses an MBL (VIM-2), OXA-1 beta-lactamase and the ESBL (GES-1) in Peru. It is also the first report of a VIM carbapenemase in Peru.

Diversity of beta-lactamases produced by ceftazidime-resistant Pseudomonas aeruginosa isolates causing bloodstream infections in Brazil

A retrospective survey was conducted to characterize beta-lactamases in a collection of 43 ceftazidime-resistant Pseudomonas aeruginosa isolates recovered from patients with bloodstream infections hospitalized at a Brazilian teaching hospital between January and December 2005. Resistance rates for carbapenems, aminoglycosides, and quinolones were over 80%, with only colistin remaining active against all isolates. Pulsed-field gel electrophoresis analysis identified seven different genotypes. AmpC overproduction was found to be the sole beta-lactamase-mediated mechanism responsible for ceftazidime resistance in four isolates (9.3%). Nine isolates (20.9%) produced an extended-spectrum beta-lactamase (ESBL), either GES-1 (n = 7, 16.3%) or CTX-M-2 (n = 2, 4.6%). Carbapenemase activity was detected in 30 (70%) additional isolates. Among those isolates, two isolates (4.6%) produced the ESBL GES-5, possessing the ability to hydrolyze imipenem; a single isolate (2.3%) produced the metallo-beta-lactamase (MBL) IMP-1; and 27 isolates produced the MBL SPM-1 (62.8%). None of the isolates coproduced both ESBL and MBL. Insertion sequence elements ISCR4 and ISCR1 were associated with bla(SPM-1) and bla(CTX-M-2) genes, respectively, whereas the bla(GES-1) and bla(GES-5) genes were part of class 1 integron structures. This study underlines the spread of MBL- and ESBL-producing P. aeruginosa isolates as an important source of ceftazidime resistance in Brazil.